Eugeost scmtjrek



Patented Dec. 22, v1925i.

UNITED STATES PATENT OFFICE.

EUeEN scHnER, 0F coLoGNE-MULHEIM,

GERMANY; nssieivon To FELTEN 'AND MANY.

METHOD OF EQUALIZING PAIRS OF SELF-INDUCTIONCOILS.

Application filed March 28, 1922.

To @El whom t may concern:

Be it known that I, EUGEN SGHRER, a citizen of Germany, residing at Coloo'ne- Mulheim, Prinz-Wilhelmstrasse 71, ermany, have invented new and useful Improvements in Methods of Equalizing Pairs of Self-Induction Coils, of which the following is a specification.

German Patent No. 329,481 describes a pair of self-induction coils for loading tourwire telephone cables according to the Pupin system, in which, inside of aprotectingframe ot laminated iron, two coils are arranged on both sides of a ring-shaped disc, and are connected magnetically with this disc at the pole-places by means of iron fillets (connectors). The two coils, as sidecoils, load, each for itself, one of the two side-circuits, and likewise the phantom-circuit by action of the magnetic fieldowing in this case through both coils jointly. The winding of the coils therefore determines the amount of self-induction which the coilpair supplies both for the sideand phantom circuits.

It is well known that in order to prevent cross-talk between the three circuits, it is essential, besides other conditions, that leadand return-lines of loaded circuits have equal amounts of self-induction. The coilpair, therefore, requires to be equalized in a manner thatnot only the halves of each side-coil, but also that the side-coils as halves of the coil-pair in phantom-connec-v tion Jfurnish respectively equal amounts ot self-induction.

As far as the halves of the side-coils are concerned, this can be attained easily by equalizing adequately the windings. There are difficulties arising, however, it' at the same time the coils are to be equalized on equal amounts of their self-induction for the phantom-circuit. In this case equalizationcannot be done by altering the windings, because otherwise either the equalization of the halves of the side-coils, or (by alteringboth halves by the same number of windings) the side-inductivity of the coils would again be altered. Equalization could be done only in a manner that the ends of the winding-halves of the coil to be equalized were wound jointly round such parts of the coil-pair that they cover only the duplexeld. For this purpose the illets,` connectdifferent views.

Serial No. 547,494.

The invention provides another means for.

this equalization, which, as is shown in the Jfollowing, is considerably simpler and more reliable.

As mentioned above, the coil-pair is placed inside an iron Vinduction-protecting-frame, which encloses the coils. The diagram represents the coil-pair with its frame in two In these ligures l and 2 represent the two side-coils of the pair, Z represents the disc, S and S represent the iron connecting-lillets, and R the external protecting-frame.. The protective eiiect of ther frame consists in that it absorbs the outer leakage-fields eiiusin g by the phantomcurrents out of the illet-pointsof the coils, preventing hereby their further spreading outward.

Now, these leakage-fields contribute a small amount to the phantom-self-induction of each coil, i. e. to the halves of the total phantom-self-induction. It is evident that by shifting the coil-pair within the frame in a mannerthat it approaches `more or less the one or the other of the long sides of' the trame, the leakage-ields iiowing through the frame, and in consequence the small contributions to the halves of the phantom-selfinduction, may be strengthened or weakened. For, in consequence of this shifting, the aerial distances between the coil-poles and the frame, and lconsequently the magnetic resistances of the leakage-fields on each side of the pair, change in a. reversed sensey According to the invention, the equalization of the halves of the phantom-self-induction of the coil-pair is eii'ected in such manner that the pair inside the frame is shifted towards one of the long sides so that the two amounts of vthe phantom-self-induction belonging to each coil, becomes equal. A The equality for instance in this case is ascertained by measurements (f. i. in a Wheatstone-bridge), as with the equalization of the halves of the side-coils.

What I claim is:

Apparatus for equalizing the self-induction in the pair of coils for loading four wire telephone lines. comprising in combination a. protective induction frame of magioo netic material, an annular disc:y Within said frame, two selff-i'ndlotionscoiils a'lsogamwnged Within said frame, one on each Side/0i the disc, and iron connectors between the poles of theeols andV the dise, said Coils being adaptedto be shifted towards one or the other of the longitudinal sides of the frame,

.equalized 10 The foregoing specification signed at Golognen Germany, `this 6th day of 'March EUGEN SGHRER. 

